Cytoplasmic Connexions between Angiosperm Meiocytes

Abstract

Massive cytoplasmic connexions are formed between the meiocytes in the anthers of several asngiosperm species studied electron microscopically. These cytomictic channels are initiated in the pre-leptotene period, and persist throughout the meiotic prophase. They disappear before meiosis II, after which the spores become totally isolated within the callose tetrad wall. The channels are mostly cylindrical, ranging in diameter between 0.5 and 1.5μ. They may account for as much as 24 per cent of the interface between neighbouring meiocytes. Nuclear material (DNA) may pass through the channels the phenomenon termed ‘cytomixis’ by Gates-but seemingly only in consequence of handling. However, the passage of elements of the endoplasmic reticulum and cytoplasmic organelles probably occurs in vivo, and it is suggested that the whole archesporium in a single loculus behaves as a giant coenocyte, throughout which cyclosis occurs. The role of the cytomictic channels is presumably connected with the movement of materials during the meiotic prophase. The presence of the channels accounts for the synchroneity of the mother-cell nuclei in the meiotic division, and also for the sensitivity of anthers to injury. Mechanical damage commonly results in complete sterilization, evidently because of the traumatic effect on the whole linked-cell mass. The inter-dependence of the mother cells also explains why attempts to culture isolated meiocytes from early stages in vitro have been unsuccessful.